So big was the leak that it might have caused us to lose World War II. So mysterious is the identity of the leaker that we can’t be sure to this day who it was…or at least not entirely sure.

Blazoned in huge black letters across page one of the December 4, 1941, issue of the Chicago Tribune was the headline: F.D.R.’S WAR PLANS! The Times Herald, the Tribune ’s Washington, D.C., ally, carried a similarly fevered banner. In both papers Chesly Manly, the Tribune's Washington correspondent, revealed what President Franklin D. Roosevelt had repeatedly denied: that he was planning to lead the United States into war against Germany. The source of the reporter’s information was no less than a verbatim copy of Rainbow Five, the top-secret war plan drawn up at FDR’s order by the Joint Board of the Army and Navy.

Manly’s story even contained a copy of the President’s letter ordering the preparation of the plan. The reporter informed the Tribune and Times Herald readers that Rainbow Five called for the creation of a ten-million-man army, including an expeditionary force of five million men that would invade Europe to defeat Hitler. To all appearances the story was an enormous embarrassment to a President who when he ran for a third term in 1940 had vowed that he would never send American boys to fight in a foreign war.

It also made a fool or a liar out of Sen. Alben Barkley, the Senate majority leader. On August 18, 1941, after Roosevelt and Churchill had met in Placentia Bay, Newfoundland, Manly had written a story based on another leak, reporting, without documentation, plans for an American expeditionary force. The next day, Barkley had risen in the Senate and denounced Manly for writing a “deliberate and intentional falsehood.”

In Congress antiwar voices rose in protest. Alarmed Democratic House leaders delayed consideration of the administration’s $8.244 billion arms bill for more than two hours. Republican Congressman George Holden Tinkham of Massachusetts declared that the nation had been “betrayed” and received unanimous consent for his motion to put the story into the Congressional Record . “The biggest issue before the nation today is the Tribune story,” said Republican Congressman William P. Lambertson of Kansas. “If it isn’t true, why doesn’t the President deny it?” In the Senate, Burton K. Wheeler, a Democrat from Montana and the leading antiwar spokesman, who had predicted Roosevelt would “plow under every fourth American boy,” declared that the story proved everything he had been saying.

Although Hitler had crushed France and the rest of Europe except for Great Britain and was now advancing through Russia, most Americans felt no great desire to stop him. The threat from Japan seemed even more remote, although the Japanese were clearly on the march to dominate Asia. Since 1937 their war with China had given them control of virtually the entire Chinese coast. In the summer of 1941 they had seized French Indochina. A majority of Americans favored aid to China and Great Britain, but polls revealed that 80 percent were opposed to declaring war on Germany or Japan. Many viewed with great uneasiness Roosevelt’s policy of escalating belligerence with Germany, which had U.S. Navy ships convoying war supplies as far east as Iceland and had already produced three clashes between U-boats and American destroyers.

Congress reflected this public ambivalence. On August 13, 1941, the House of Representatives had come within a single vote of refusing to extend the 1940 Draft Act. Only an all-out effort by the White House staff prevented a catastrophic political defeat. On September 11 Roosevelt reported that the USS Greer had been attacked by a German submarine and henceforth U.S. ships had orders to “shoot on sight” any German vessel in the proclaimed neutral zone west of Iceland. The President neglected to say that Greer had stalked the sub for three hours, in cooperation with a British patrol plane. As recently as October 27, 1941, Roosevelt had been reduced to using a map, forged by British intelligence, purporting to be a German plan to conquer South America. Without this device he would never have persuaded Congress to relax the Neutrality Act to let American vessels carry arms to British ports.

If the Tribune story caused consternation in Congress, its impact at the War Department could be described as explosive. The man who has provided the most vivid recollection is Gen. Albert C. Wedemeyer. “If I live to be a hundred,” he told me when I interviewed him in the spring of 1986, “December fifth, 1941, will still seem like yesterday.” Although only a major in the War Plans Division, Wedemeyer had already been tabbed by his superiors as a man with a bright future. In 1936 they had sent him to Germany, where he spent two years studying at the German War College in Berlin. When Roosevelt ordered the preparation of Rainbow Five, the forty-four-year-old major was given the task of writing it.